The invention relates to a resistance material comprising a mixture of a permanent binder, a temporary binder and a resistance-determining component which is a metal rhodate. The invention also relates to a resistor having a resistor body provided with leads, the resistor body having been produced by heating a substrate bearing such a resistance material so as to remove the temporary binder.
Such a resistance material is described in UK Pat. No. 1,535,139 (U.S. Pat. No. 4,107,387) in which the resistance-determining component is a metal rhodate having a composition defined by the formula M.sub.3 Rh.sub.7 O.sub.15, M preferably being Pb or Sr.
Compared to many oxidic compounds previously suggested for use as the resistance-determining component in resistance materials, this compound has the advantage that it is a completed-reaction product which, with a permanent binder and, possibly, together with another resistance-determining component having a different temperature dependence of resistance, can be processed in a simple manner on a suitable substrate to form a resistor body. Prior to the development of these resistance-materials, resistance pastes were available in which the resistance-determining component was not obtained until the paste had been fired on a substrate, a noble metal oxide reacting during the firing process with a vitreous binder, for example a lead oxide glass, which noble metal oxide and vitreous binder were present in the paste. This required a rather long firing time (for example, half an hour) at a relatively high temperature (approximately 800.degree. C.).
A further advantage of the above mentioned M.sub.3 Rh.sub.7 O.sub.15 materials is the small negative temperature coefficient of resistance (TCR) of these materials, which temperature behavior is rare. Combining one of these materials with a material having a linear, positive temperature coefficient of resistance (which materials are much commoner than negative TCR materials) makes it possible to produce resistors having a very low TCR (.vertline.TCR.vertline.&lt;100.times.10.sup.-6 .vertline..degree.C. in a temperature range from -100.degree. to +200.degree. C.).